/*
 * ------------------------------------------------------------------------
 *
 *  Copyright by KNIME AG, Zurich, Switzerland
 *  Website: http://www.knime.com; Email: contact@knime.com
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License, Version 3, as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, see <http://www.gnu.org/licenses>.
 *
 *  Additional permission under GNU GPL version 3 section 7:
 *
 *  KNIME interoperates with ECLIPSE solely via ECLIPSE's plug-in APIs.
 *  Hence, KNIME and ECLIPSE are both independent programs and are not
 *  derived from each other. Should, however, the interpretation of the
 *  GNU GPL Version 3 ("License") under any applicable laws result in
 *  KNIME and ECLIPSE being a combined program, KNIME AG herewith grants
 *  you the additional permission to use and propagate KNIME together with
 *  ECLIPSE with only the license terms in place for ECLIPSE applying to
 *  ECLIPSE and the GNU GPL Version 3 applying for KNIME, provided the
 *  license terms of ECLIPSE themselves allow for the respective use and
 *  propagation of ECLIPSE together with KNIME.
 *
 *  Additional permission relating to nodes for KNIME that extend the Node
 *  Extension (and in particular that are based on subclasses of NodeModel,
 *  NodeDialog, and NodeView) and that only interoperate with KNIME through
 *  standard APIs ("Nodes"):
 *  Nodes are deemed to be separate and independent programs and to not be
 *  covered works.  Notwithstanding anything to the contrary in the
 *  License, the License does not apply to Nodes, you are not required to
 *  license Nodes under the License, and you are granted a license to
 *  prepare and propagate Nodes, in each case even if such Nodes are
 *  propagated with or for interoperation with KNIME.  The owner of a Node
 *  may freely choose the license terms applicable to such Node, including
 *  when such Node is propagated with or for interoperation with KNIME.
 * ---------------------------------------------------------------------
 *
 */
package org.knime.core.ui.node.workflow.lazy;

import java.util.concurrent.CompletableFuture;

import org.knime.core.ui.node.workflow.NodeContainerUI;
import org.knime.core.ui.node.workflow.WorkflowManagerUI;

/**
 * A workflow manager that isn't complete on instantiation and requires to (down-)load data (only once) before all
 * methods can be used. If a method is called without loading ({@link #load()}) the workflow manager first, a
 * {@link NotLoadedException} will be thrown. Methods derived from the parent interface {@link NodeContainerUI} can be
 * called without loading!
 *
 * The actual use case: (Wrapped) metanodes in a workflow (that are {@link WorkflowManagerUI}-instances themselves)
 * usually are not loaded entirely - i.e. the node's data (name, ports etc.) is available but not the workflow they
 * contain. When a method is called that accesses information of the contained workflow (e.g. contained nodes etc.), it
 * needs to be loaded first by calling {@link #load()}.
 *
 * @author Martin Horn, KNIME GmbH, Konstanz, Germany
 */
public interface LazyWorkflowManagerUI extends WorkflowManagerUI {

    /**
     * @return <code>true</code> if {@link #load()} has been called at least once with success, otherwise
     *         <code>false</code>
     */
    boolean isLoaded();

    /**
     * (Down-)loads the data necessary to be able to call all methods of the workflow manager. If this method returns
     * successfully, the workflow manager methods don't fail with a {@link NotLoadedException} anymore.
     *
     * @return the future that carries out the loading
     */
    CompletableFuture<Void> load();

}
